Shadows of the abandoned hospital

You are a group of journalists who have received an anonymous letter asking you to conduct a small investigation in an old, abandoned private psychiatric clinic. 20 years ago, there was a fire. Unfortunately, it was not possible to restore it, so the owner decided to close the clinic. However, people living near it see lights on in it every night, and some even hear loud screams. The letter only contained an address. Your task is to find out what happens here at night...